Near Field Optical Microscopy in Periodically Poled LiNbO₃and LiTaO₃Superlattices

Optical studies of ferroelectric and ferroelastic domain walls

“…Microscopy techniques are called super-resolved when they are able to overcome the diffraction limit, which can be done notably by working in the near-field regime. They are of course very appealing for the studies of domain walls, but can be very challenging both in their implementation and interpretation [142][143][144][145][146][147][148][149][150][151][152][153][154][155][156][157][158].…”

“…Near-field scanning optical microscopy (NSOM, or SNOM) has been used to image domain structures in several ferroelectrics [142][143][144][145][146][147][148][149][150][151][152][153][154], with contrast observed at domain walls in LiTaO 3 [142,150,151], LiNbO 3 [147,148], TGS [143,153], BaTiO 3 [144] and Ba 2 NaNb 5 O 15 [147]. These measurements have been performed in different modes of operation.…”

“…Finally, in the reflection mode, the sample is still illuminated with a fiber but the light is collected in reflection by an objective [146,147,153]. The small aperture of the fiber (typically a hundred of nanometers) and the use of a metal coating to force the light to enter the aperture, allows spatial resolutions better than a fifth of a wavelength of light [146,[148][149][150]152].…”

“…This might be the reason for the large spatial extension of features observed at domain walls with these modes [142-144, 147, 148, 150, 151]. On top of that, small differences in refractive index between domains make them act as waveguides with light confined in the high refractive index regions and as a consequence concentrated at certain spots [147,149,159,160].…”

Optical studies of ferroelectric and ferroelastic domain walls

“…Microscopy techniques are called super-resolved when they are able to overcome the diffraction limit, which can be done notably by working in the near-field regime. They are of course very appealing for the studies of domain walls, but can be very challenging both in their implementation and interpretation [142][143][144][145][146][147][148][149][150][151][152][153][154][155][156][157][158].…”

“…Near-field scanning optical microscopy (NSOM, or SNOM) has been used to image domain structures in several ferroelectrics [142][143][144][145][146][147][148][149][150][151][152][153][154], with contrast observed at domain walls in LiTaO 3 [142,150,151], LiNbO 3 [147,148], TGS [143,153], BaTiO 3 [144] and Ba 2 NaNb 5 O 15 [147]. These measurements have been performed in different modes of operation.…”

“…Finally, in the reflection mode, the sample is still illuminated with a fiber but the light is collected in reflection by an objective [146,147,153]. The small aperture of the fiber (typically a hundred of nanometers) and the use of a metal coating to force the light to enter the aperture, allows spatial resolutions better than a fifth of a wavelength of light [146,[148][149][150]152].…”

“…This might be the reason for the large spatial extension of features observed at domain walls with these modes [142-144, 147, 148, 150, 151]. On top of that, small differences in refractive index between domains make them act as waveguides with light confined in the high refractive index regions and as a consequence concentrated at certain spots [147,149,159,160].…”

Optical studies of ferroelectric and ferroelastic domain walls

“…Microscopy techniques are called super-resolved when they are able to overcome the diffraction limit, which can be done notably by working in the near-field regime. They are of course very appealing for the studies of domain walls, but can be very challenging both in their implementation and interpretation [142][143][144][145][146][147][148][149][150][151][152][153][154][155][156][157][158].…”

“…Near-field scanning optical microscopy (NSOM, or SNOM) has been used to image domain structures in several ferroelectrics [142][143][144][145][146][147][148][149][150][151][152][153][154], with contrast observed at domain walls in LiTaO 3 [142,150,151], LiNbO 3 [147,148], TGS [143,153], BaTiO 3 [144] and Ba 2 NaNb 5 O 15 [147]. These measurements have been performed in different modes of operation.…”

“…Finally, in the reflection mode, the sample is still illuminated with a fiber but the light is collected in reflection by an objective [146,147,153]. The small aperture of the fiber (typically a hundred of nanometers) and the use of a metal coating to force the light to enter the aperture, allows spatial resolutions better than a fifth of a wavelength of light [146,[148][149][150]152].…”

“…This might be the reason for the large spatial extension of features observed at domain walls with these modes [142-144, 147, 148, 150, 151]. On top of that, small differences in refractive index between domains make them act as waveguides with light confined in the high refractive index regions and as a consequence concentrated at certain spots [147,149,159,160].…”

Optical studies of ferroelectric and ferroelastic domain walls

“…Microscopy techniques are called super-resolved when they are able to overcome the diffraction limit, which can be done notably by working in the near-field regime. They are of course very appealing for the studies of domain walls, but can be very challenging both in their implementation and interpretation [142][143][144][145][146][147][148][149][150][151][152][153][154][155][156][157][158].…”

“…Near-field scanning optical microscopy (NSOM, or SNOM) has been used to image domain structures in several ferroelectrics [142][143][144][145][146][147][148][149][150][151][152][153][154], with contrast observed at domain walls in LiTaO 3 [142,150,151], LiNbO 3 [147,148], TGS [143,153], BaTiO 3 [144] and Ba 2 NaNb 5 O 15 [147]. These measurements have been performed in different modes of operation.…”

“…Finally, in the reflection mode, the sample is still illuminated with a fiber but the light is collected in reflection by an objective [146,147,153]. The small aperture of the fiber (typically a hundred of nanometers) and the use of a metal coating to force the light to enter the aperture, allows spatial resolutions better than a fifth of a wavelength of light [146,[148][149][150]152].…”

“…This might be the reason for the large spatial extension of features observed at domain walls with these modes [142-144, 147, 148, 150, 151]. On top of that, small differences in refractive index between domains make them act as waveguides with light confined in the high refractive index regions and as a consequence concentrated at certain spots [147,149,159,160].…”